Chimpanzee taxonomy remains an active area of research. Four subspecies are commonly recognized: the West African Chimpanzee Pan troglodytes verus; the Nigeria-Cameroon Chimpanzee P. t. ellioti; the Central Chimpanzee P. t. troglodytes; and the Eastern Chimpanzee P. t. schweinfurthii. Recent mitochondrial DNA work (Gonder et al. 2006) shows that schweinfurthii is embedded in troglodytes, and suggests that there are only two major clades of chimpanzees: Pan troglodytes ellioti in West Africa and P. t. troglodytes in Central and East Africa. Based on recent nuclear DNA work, as well as considerations of the overall similarity in behaviour and morphology of the proposed subspecies, Fischer et al. (2006) argue that differences between chimpanzee populations are too small to warrant subspecific designations. While the appropriate taxonomic labelling for different chimpanzee populations remains unresolved, the relative importance of different threats faced by chimpanzees varies across Africa, making a regional approach valuable for conservation purposes. We, therefore, use a four-subspecies classification system here, recognizing that future work may lead to a consensus recognizing more or fewer subspecies.

Justification:
Although Chimpanzees are the most abundant and widespread of the apes, with many populations in protected areas, the declines that have occurred are expected to continue to occur, satisfy the criteria for ranking as Endangered (Oates 2006). Due to high levels of exploitation, loss of habitat and habitat quality due to expanding human activities, this species is estimated to have experienced a significant population reduction in the past 20 to 30 years (one generation is estimated to be 20 years; Boesch and Boesch-Achermann 2000, Emery Thompson et al. in prep., Gombe long-term records, unpubl.) and it is suspected that this reduction will continue for the next 30 to 40 years. The maximum population reduction over a three-generation (i.e., 60 year) period from the 1970s to 2030 is suspected to exceed 50%, hence qualifying this taxon for Endangered under criterion A4. The causes of the reduction, although largely understood, have certainly not ceased and are not easily reversible. The suspected future continuation of the population reduction is a precautionary approach based on the rapidly increasing human population density in the region, the spread of diseases such as Ebola, and the degree of political instability in some range states.

Chimpanzees have a wide but discontinuous distribution in Equatorial Africa between 13 degrees North and 7 degrees South. They occur from southern Senegal across the forested belt north of the Congo River to western Uganda and western Tanzania, from sea-level to 2,800 m asl. The four subspecies recognized here are distributed as follows:

P. t. verus (Schwarz, 1934) is found in West Africa from Senegal to Nigeria.

P. t. ellioti (Gray, 1862) is found only in Nigeria and Cameroon, north of the Sanaga River.

P. t. troglodytes (Blumenbach, 1799) ranges from Cameroon, south of the Sanaga River, to the Congo River/Ubangi River (Democratic Republic of Congo).

P. t. schweinfurthii (Giglioli, 1872) ranges from the Ubangi River/Congo River in Central African Republic and the Democratic Republic of the Congo, to western Uganda, Rwanda and western Tanzania (with small, relict populations in Burundi and southeastern Sudan).

Little recent survey work has been carried out over much of the chimpanzee’s range, and so population estimates are crude. The most recent estimate of total population size is 172,700 to 299,700 (Butynski 2003). Approximately 6,400 to 9,600 eastern chimpanzees were estimated to occur outside the DRC, with about 5,000 in Uganda. DRC was estimated to have 70,000 to 110,000. Central African chimpanzees were estimated to number 70,000 to 116,500. In the west, P. t. verus is patchily distributed and number between 21,300 and 55,600 with the greatest number estimated to be found in Guinea (Kormos et al. 2003); P. t. ellioti is the least numerous taxon with a total population of less than 6,500 individuals remaining (B. Morgan and J. Oates pers. comm. 2006). The only relatively large and secure population of P. t. ellioti is in Gashaka-Gumti National Park in Nigeria, with an estimated population of up to 1,500 (Oates et al. 2003).

Chimpanzees are found predominantly in moist and dry forests, and forest galleries extending into savanna woodlands. They are omnivorous, and their diet is highly variable according to individual populations and seasons. Fruit comprises about half the diet, but leaves, bark, and stems are also important. Mammals comprise a small but significant component of the diet of many populations. Chimpanzees form social communities of 5 to 150 animals. Home ranges are larger in woodland forest mosaics than in mixed forest, and average 12.5 km² (range 5 to 400 km²).

The four subspecies face similar threats but to varying degrees in different regions.

Major threats include:1. Habitat destruction and degradation, with varying impacts on populations and caused mainly by: (a) slash and burn agriculture: deforestation across West and Central Africa has severely reduced chimpanzee habitats. It is estimated that more than 80% of the region’s original forest cover has been lost (Kormos et al. 2003). Rapid growth in human populations across Africa is expected to lead to continued widespread conversion of forest and woodland to agricultural land.(b) Logging, oil and gas mining: increased accessibility to remote areas through road building poses a risk to chimpanzee populations through habitat degradation and fragmentation and potential increased poaching in areas previously not seriously impacted by such anthropogeniic pressures. In western Central Africa deforestation rates are low but selective logging is, or will be, carried out in the majority of forests outside of national parks. Logging generally, but not always, has a negative impact on chimpanzee density due to habitat alteration (removal of important food trees) and disturbance (Plumptre and Johns 2001, White and Tutin 2001).

2. Poaching. Due to low population densities and slow reproductive rates, hunting often leads to the rapid local extirpation of chimpanzee populations. The main reasons for hunting are:(a) for meat: Chimpanzees currently constitute 1 to 3% of bushmeat sold in urban markets in Côte d’Ivoire (Caspary et al. 2001), and commercial hunting, often facilitated by logging, has caused declines in chimpanzee populations in some areas (Wilkie and Carpenter 1999, Tutin et al. 2005).(b) pet trade: Although the pet trade is illegal in all range countries that are signatories to CITES, it persists illegally across Africa. The capture of an infant chimpanzee usually implies the death of its mother and often other members of the community.(c) medicinal purposes: In some localities, chimpanzees are hunted traditionally for medicinal purposes. Some range countries, such as Guinea, still officially permit the capture of chimpanzees for scientific research.(d) snares/crop-protection: People kill chimpanzees intentionally to protect their crops (S. Kamenya pers. comm. 2007). Chimpanzees may also be maimed or killed unintentionally when caught in snares set for other animals, such as baboons or cane rats (e.g., Reynolds 2005, C. Duvall pers. comm. 2007).

3. Disease. The main cause of death in chimpanzees at Gombe, Mahale and Taï is infectious disease (e.g., Goodall 1986, Nishida et al. 2003, Hanamura et al. 2006). Because chimpanzees and humans are so similar, chimpanzees succumb to many diseases that afflict humans (Butynski 2001). The frequency of encounters between chimpanzees and humans and/or human waste is increasing as human populations expand, leading to higher risks of disease transmission between humans and chimpanzees. If not properly managed, research and tourism also presents a risk of disease transmission between humans and chimpanzees. In the past 15 years, Ebola haemorrhagic fever has killed chimpanzees in Côte d’Ivoire (Formenty 1999), and repeated epidemics have caused dramatic declines of ape populations in remote protected areas in Gabon and the Republic of Congo (Huijbregts et al. 2003, Walsh et al. 2005, P. Walsh, unpubl.). While recent surveys have not always distinguished between the nests of chimpanzees and gorillas, the pooled density of apes in several large areas has declined by 50 to 90% following Ebola epidemics (Maisels et al. 2004, Tutin et al. 2005, Bermejo et al. 2006, Lahm et al. 2006, P. Walsh, unpubl.).

Chimpanzees are listed under Appendix I of CITES and as Class A under the African Convention. Chimpanzees are protected by law in most countries and they are present in numerous national parks throughout their range, although many populations occur outside protected areas. Nonetheless, stricter enforcement of wildlife laws, and more effective management of protected areas are urgently needed. Engagement with the extractive industries are predominant in Central Africa towards curtailing the bushmeat trade is essential. Some marked success in co-management and other arrangements have been implemented and these should be duplicated and extended (Morgan and Sanz in prep.).

Conservation education and promotion of economic alternatives to hunting and land-extensive agriculture should also be supported. Major resources are required to identify appropriate conservation actions in the face of the spread of Ebola (Walsh et al. 2005). Finally, a combination of factors has led to a poor understanding of the current population status of Pan troglodytes. Much of the range has not been surveyed, survey methods have been inconsistent, and many of the surveys are now out of date. Older survey data are particularly unreliable as Ebola, commercial hunting and extractive industries are known to have caused dramatic declines in some areas (Tutin et al. 2005). New surveys using consistent methods are greatly needed throughout most of the range of Pan troglodytes (Kuehl et al. in prep.). These will enable the conservation community to better understand the true impact of Ebola, the bushmeat trade, habitat degradation and destruction, and to effectively set priorities.